Noncontact web transporting apparatus

ABSTRACT

A curved area is a jet surface for jetting the air from air jet openings formed in a zigzag state. Two rollers are disposed in parallel with a turn bar so as to be adjacent to both ends of the jet surface in a transporting direction of a web. The roller rotates, contacting with a surface opposite to a levitation surface of the web, when the web is transported. Oscillation of the web is prevented and the web is prevented from coming into contact with the turn bar. Further, the air jetted from the jet surface is prevented from leaking in the transporting direction. The air leaks in a width direction of the web. An air pressure is prevented from lowering at both ends of the jet surface so that a levitation amount of the web becomes uniform.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an apparatus for transporting a web in a noncontact manner and in a stable levitation state.

2. Description of the Related Art

A web of aluminum and so forth is transported by rollers at a line for producing a photosensitive printing plate (PS plate). At this time, a slip and contact between the web and the roller are likely to damage a web surface (coating surface of a photosensitive layer), and a quality defect is likely to be caused. In order to prevent the quality defect, it is necessary to transport the web in a noncontact manner without contacting the web surface with a roller surface. As to a noncontact transporting method, is considered a method in which the air is jutted from a transport surface of a turn bar to levitate the web. However, when this kind of the turn bar is used to levitate and transport the web, oscillation of the web causes flapping so that an air pressure lowers near both ends of the transport surface of the turn bar, and the web surface is likely to come into contact with the transport surface. It is difficult to stably transport the web in the non-contact manner and in a state that a levitation amount of the web is uniformly kept.

As mentioned above, flapping is caused due to the oscillation of the web near the ends of the transport surface of the turn bar so that the web surface comes into contact with the transport surface of the turn bar. Some methods for preventing the contact are known (see Japanese Utility-Model Laid-Open Publication Nos. 5-28632 and 6-6341, for instance). In this sort of the methods, extra air is jetted from the ends of the transport surface of the turn bar to prevent the air pressure from lowing thereat. The levitation amount of the web becomes uniform and it is hardly caused that the web surface comes into contact with the transport surface of the turn bar due to the oscillation of the web.

However, the turn bars described in the above Publication Nos. 5-28632 and 6-6341 need the extra air-amount for levitating the web. In addition, there arises a problem in that the coat increases since a structure of the turn bar becomes complicated.

SUMMARY OF THE INVENTION

In view of the foregoing, it is a primary object of the present invention to provide a noncontact web transporting apparatus, at low cost, in which oscillation of a web is reduced without complicating a structure of a turn bar to keep a levitation amount of the web in a uniform state.

In order to achieve the above and other objects, the noncontact web transporting apparatus according to the present invention comprises a turn bar for levitating the web and altering a transport direction thereof. The turn bar has a jet surface formed with a plurality of jet openings from which gaseous matter (including the air) is jetted. The gaseous matter jetted from the jet openings is sprayed to a first surface of the web. The noncontact web transporting apparatus further comprises a pair of rollers, which are disposed in parallel with the turn bar so as to be adjacent to both ends of the jet surface relative to the transport direction of the web. The roller rotates, coming into contact with a second surface of the web opposite to the first surface.

In a preferred embodiment, a winding angle of the web of which the second surface is wound on the roller is changed by a winding-angle changing mechanism. When the web has high rigidity, it is preferable to make the winding angle small.

According to the present invention, oscillation of the web is reduced at both ends of the jet surface in the web transporting direction so that flapping is prevented. Since the flapping is prevented, the web is prevented from coming into contact with the turn bar. In addition, the gaseous matter jetted from the jet surface is prevented from leaking out of both ends of the jet surface so that a gaseous-matter pressure is prevented from lowering at these ends. Thus, the pressure of the jet surface is uniformly kept so that a levitation amount of the web becomes uniform and the web is stably transported in the noncontact manner. Since the rollers are merely provided without changing a structure of the turn bar, the noncontact web transporting apparatus may be provide at low cost in comparison with a case using a turn bar in which a jet amount of gaseous matter is increased at both sides of the turn bar in the web transporting direction to prevent the web from coming into contact with the turn bar.

By setting a gap, which exists between the roller and the jet surface of the turn bar, so as to be minimum in consideration of a thickness of a web joint portion, the gaseous matter is prevented from leaking in the web transporting direction. Thus, it is prevented that the web surface comes into contact with the jet surface (transporting surface) of the turn bar due to a decline of the gaseous-matter pressure. In addition, a wasted usage-amount of the gaseous matter is reduced so that the web is efficiently levitated.

Further, since the winding-angle changing member makes the winding angle of the web small when the web has high rigidity, the web surface is prevented from coming into contact with the transporting surface of the turn bar.

BRIEF DESCRIPTION OF THE DRAWINGS

The above objects and advantages of the present invention will become apparent from the following detailed description of the preferred embodiments of the invention when read in conjunction with the accompanying drawings, in which:

FIG. 1 is a schematic illustration showing a process for producing a PS plate;

FIG. 2 is a perspective view showing a structure of a noncontact web transporting apparatus;

FIG. 3 is a perspective view showing a structure of a turn bar;

FIG. 4 is a schematic side view showing the structure of the noncontact web transporting apparatus;

FIG. 5 is a schematic side view of the noncontact web transporting apparatus of a case in that a winding angle is large; and

FIG. 6 is a schematic side view showing a structure of a conventional noncontact web transporting apparatus.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

An embodiment of the present invention is described below, referring to the drawings. FIG. 1 is a schematic illustration showing a PS-plate producing process. The PS-plate producing process 10 is performed by a surface treating apparatus 13, a washing apparatus 14, first and second coating apparatuses 15 and 16, and first and second drying apparatuses 17 and 18. A web 11 made of aluminum is advanced from a web roll 19, which is a source of the web, by a web feeding apparatus 20. And then, the web 11 is forwarded to the surface treating apparatus 13 by a plurality of rollers 21. In the surface treating apparatus 13, surface treatment is carried out in order to improve coatability and adhesion of a photosensitive compound to be applied to a surface of the web 11. The web 11 for which the surface treatment has been carried out is cleaned by the washing apparatus 14. Successively, a photosensitive coating liquid is applied to the web 11 by the first coating apparatus 15.

The web 11 coated by the first coating apparatus 15 is forwarded to the first drying apparatus 17 to dry a coating surface thereof. A noncontact web transporting apparatus 22 is used for transporting the web 11 from the first drying apparatus 17 to the second coating apparatus 16. The noncontact web transporting apparatus 22 comprises a turn bar 23 and four rollers 24 a and 24 b. The turn bar 23 levitates the web 11 to transport it in a noncontact manner. In virtue of this, the coating surface, which has high adhesive properties even after drying, is dealt with in the noncontact manner up to the second coating apparatus 16. A coating liquid for a protector layer is applied to the web 11 in the second coating apparatus 16. Successively, the web 11 is dried in the second drying apparatus 18. And then, the web 11 is transported by a plurality of rollers 25. After that, the web 11 is taken up around a core 27 by a web take-up apparatus 26. Incidentally, the present invention is not exclusive to the embodiment shown in FIG. 1.

Next, a structure of the noncontact web transporting apparatus 22 is described below with FIGS. 2, 3 and 4. FIG. 2 is a perspective view showing the structure of the noncontact web transporting apparatus 22. FIG. 3 is a perspective view showing a structure of the turn bar 23. FIG. 4 is a schematic side view of the noncontact web transporting apparatus 22. As described above, the transporting apparatus 22 comprises the turn bar 23 and the four rollers 24 a and 24 b. The turn bar 23 comprises a transporting portion 35 having a substantially U-shaped cross section. The transporting portion 35 constitutes a front side, a rear side and an upper side of the turn bar 23. The turn bar 23 further comprises two side walls 36, 37 and a bottom plate 38. The side walls 36 and 37 constitute lateral sides and cover both ends of the transporting portion 35. The bottom plate 38 constitutes a lower side and covers the bottom of the transporting portion 35. The inside of the turn bar 23 is hollow. Incidentally, the web 11 is transported by the transporting portion 35.

The transporting portion 35 comprises a curved area 35 a bending in an arc shape, and plane areas 35 b extending from both edges of the curved area 35 a along a transporting direction of the web. The curved area 35 a is a jet surface for jetting the air to levitate and transport the web 11. All over the curved area 35 a, air jet openings 39 having a same size are formed at predetermine intervals in a zigzag state. In this embodiment, the interval of the air jet openings 39 is 10.0 mm in the web transporting direction, and the horizontal interval thereof is 10.5 mm. The present invention, however, is not limited to the above-noted intervals of the air jet openings 39 and the shape thereof. Incidentally, regarding the air jet openings 39 shown in the drawing, the size and the intervals thereof are magniloquently illustrated for the purpose of avoiding complication.

The side walls 36 and 37 are respectively provided with air ducts 40 a and 40 b through which the air is supplied into the turn bar 23 by means of a blower or the kike, which is not shown. Thus, an inner pressure of the turn bar 23 increases and becomes higher than the outer pressure so that the air is jetted from the air openings 39. In this way, the air is jetted from the jet openings 39 to levitate the web 11. The levitated web 11 is transported in the noncontact manner by means of the turn bar 23. Incidentally, the gaseous matter to be jetted from the turn bar 23 is not limited to the air. The other gaseous matter may be used.

The two rollers 24 a are disposed in parallel with the turn bar 23 so as to be adjacent to both ends of the curved area 35 a, which is the air jet surface. The roller 24 a rotates, coming into contact with a surface opposite to the levitation surface of the web 11. In virtue of this, oscillation of the web 11 is reduced at both ends of the air jet surface so that flapping is prevented. Thus, it is possible to prevent the surface of the web 11 from coming into contact with the transporting surface of the turn bar 23. Further, by narrowing a gap d, as much as possible, between the roller 24 a and the transporting portion 35 (air jet surface) of the turn bar 23, it is possible to prevent the air, which is jetted from the curved area 35 a of the turn bar 23, from leaking in the transport direction of the web 11. Incidentally, in order to avoid the contact of the surface of the web 11 and the transport surface of the turn bar 23, it is preferable that the gap d is longer than a maximum thickness of the web 11 by a prescribed amount.

The other two rollers 24 b are disposed at a passage of the web 11 located below the turn bar 23. The rollers 24 b are disposed in parallel to the turn bar 23 so as to be symmetrical relative to the turn bar 23. An interval of the rollers 24 b is adapted to be longer than that of the rollers 24 a.

As shown in FIG. 6, a conventional noncontact web transporting apparatus 50 has two rollers 24 b disposed below the turn bar 23. However, a distance between the turn bar 23 and the two rollers 24 b is long so that the web 11 transported between them can freely move. When the web 11 greatly oscillates at both sides of the turn bar 23 (near an entrance side and an exit side thereof) the web 11 is in danger of coming into contact with the turn bar 23. Moreover, large quantity of the air leaks in the transporting direction of the web 11 so that a portion having an extremely small amount of levitation occurs due to reduced pressure. Thus, sometimes the surface of the web 11 contacts with the surface of the turn bar 23.

However, as described above, the rollers 24 a are adjacent to both ends of the curved area 35 a being as the air jet surface. Further, the rollers 24 a are disposed so as to be parallel with the turn bar 23. Since the rollers 24 a abut on the surface of the web 11 at both ends, movement of the web 11 is regulated. Thus, the oscillation of the web 11 is prevented and the web 11 is prevented from coming into contact with the turn bar 23. In addition, it is prevented that the air leaks in the web transporting direction due to the oscillation of the web 11. The air jetted from the air jet openings 39 flows in a width direction of the web 11 such as shown by arrows in the drawing. For making the jetted air contribute to the levitation of the web 11, it is effective that the air flows in the width direction of the web 11. The levitation amount of the web 11 becomes uniform relative to the transporting portion 35 so that the web 11 is stably transported in the noncontact manner.

The web 11 is made of aluminum and has high rigidity. When a winding angle of the web 11 is large at the rollers 24 a disposed at both ends of the air jet surface, there is a high possibility, because of the rigidity, that the web 11 approaches the web transporting surface of the turn bar 23 to come into contact therewith. In view of this, as shown in FIG. 4, shifting mechanisms 42 are provided for the respective rollers 24 b. The shifting mechanism 42 horizontally moves the roller 24 b in a right-and-left direction to change the winding angle, which is the angle of the web 11 wound on the roller 24 a. Both of the rollers 24 b are horizontally moved by the shifting mechanisms 42 from a state in that the winding angle is θ1 shown in FIG. 4. By lengthening the interval of the rollers 24 b, the winding angle becomes θ2 from θ1 such as shown in FIG. 5 so that the winding angle increases (θ1<θ2).

In this way, it is possible to change the winding angle of the web 11 relative to the roller 24 a by means of the shifting mechanism 42. When the web is made of aluminum and has high rigidity, the smaller winding angle θ1 is set by the shifting mechanism 42, such as shown in FIG. 4. In a case that the web is made of a material having low rigidity, the larger winding angle θ2 is set such as shown in FIG. 5. In virtue of this, it is possible to reduce the winding angle of the web 11 relative to the roller 24 a when the web of the high-rigidity material is levitated and transported. Thus, the web 11 is prevented from approaching the transporting surface of the turn bar 23 so that the surface of the web 11 is prevented from coming into contact with the transporting surface of the turn bar 23. By the way, in the case that the web has low rigidity, the winding angle of the web relative to the roller 24 a is not restricted. In this case, the winding angle may be properly adjusted by the shifting mechanism 42.

The shifting mechanism 42 horizontally moves the roller 24 b to change the winding angle of the web 11 relative to the roller 24 a. However, this is not exclusive. For example, the roller 24 b may be vertically moved to change the winding angle. Alternatively, the roller 24 b may be swingably moved to change the winding angle.

Next, an operation of the noncontact web transporting apparatus 22 having the above structure is described below. As to the actual PS plate, the web 11 has a maximum thickness of 0.5 mm. When joining these webs 11 with a tape, the webs 11 are overlapped and attached together with a two-sided tape, and then, an aluminum evaporation tape is pasted around an outer circumference of the joint portion for the purpose of reinforcement. As a result, a thickness of the joint portion becomes about 2.0 mm. Meanwhile, the levitation amount of the web 11 is about 2.0 mm. In consideration of this, it is determined that the gap d between the surface of the roller 24 a and the transporting surface of the turn bar 23 (the surface of the transporting portion 35) is about 4.0 mm. By doing so, the web 11 is stably levitated and transported in a state that the oscillation of the web 11 is minimized and the levitation amount is prevented from decreasing at both ends of the curved area 35 a, which is the air jet surface.

Ultimately, both of the rollers 24 a are disposed in parallel with the turn bar 23 such that the gap d is about 4.0 mm and the rollers 24 a are adjacent to both ends of the curved portion 35 a (air jet surface) of the turn bar 23 in the web transporting direction.

The web 11 is transported by the noncontact web transporting apparatus 22 along the passage formed by the rollers 24 a, the rollers 24 b and the turn bar 23. At this time, the roller 24 a rotates, abutting on the surface of the web 11 opposite to the levitation surface thereof. Owing to this, the oscillation of the web 11 is prevented at each side of the turn bar 23 in the web transporting direction (at the entrance side and the exit side of the web 11) so that flapping is prevented. Thus, the web 11 is prevented from coming into contact with the transporting surface of the turn bar 23.

Meanwhile, the air jetted from the air jet surface is prevented from leaking in the web transporting direction, and leaks in the width direction of the turn bar 23 such as shown in FIG. 2. Consequently, the air pressure is prevented from lowering at both ends of the curved area 35 a (air jet surface). Thus, the levitation amount of the web 11 is uniformly kept relative to the transporting portion 35 and the web 11 is stably levitated and transported without coming into contact with the transporting surface of the turn bar 23.

In the above embodiment, the noncontact web transporting apparatus comprises the sole turn bar. However, this is not exclusive. The noncontact web transporting apparatus may comprise a plurality of turn bars. In this case, the two rollers may be disposed every turn bar in parallel therewith so as to be adjacent to both ends of the air jet surface of the turn bar in the web transporting direction.

Moreover, in the above embodiment, the noncontact web transporting apparatus 22 is disposed between the first coating apparatus 15 and the second coating apparatus 16 to transport the web 11 in the noncontact manner. However, this is not exclusive. The present invention may be adopted to transport the web in the other various apparatuses of the drying apparatus, the coating apparatus and so forth.

Further, in the above embodiment, the PS plate is transported in the noncontact manner. However, this is not exclusive. The present invention may be applicable to continuous strips having flexibility, for example, a photo-film base, a baryta paper of a photographic paper, a recording-tape base, a videotape base, a floppy-disk (registered trademark) base, and so forth.

Although the present invention has been fully described by way of the preferred embodiments thereof with reference to the accompanying drawings, various changes and modifications will be apparent to those having skill in this field. Therefore, unless otherwise these changes and modifications depart from the scope of the present invention, they should be construed as included therein. 

1. A noncontact web transporting apparatus for transporting a web in a noncontact manner, said noncontact web transporting apparatus comprising: a turn bar for levitating said web and altering a transport direction thereof, said turn bar having a jet surface formed with a plurality of jet openings from which gaseous matter is jetted, and the gaseous matter jetted from said jet openings being sprayed to a first surface of said web; and a pair of first rollers disposed so as to be parallel with said turn bar, said first rollers being adjacent to both ends of said jet surface relative to the transport direction of said web to rotate, coming into contact with a second surface of said web opposite to said first surface.
 2. A noncontact web transporting apparatus according to claim 1, further comprising: a winding-angle changing mechanism for changing a winding angle of said web of which said second surface is wound on said roller, said winding-angle changing mechanism decreasing said winding angle when said web has high rigidity.
 3. A noncontact web transporting apparatus according to claim 2, wherein said winding-angle changing mechanism comprising: a pair of second rollers disposed at a passage of said web located below said turn bar, said second rollers being also disposed so as to be parallel with said turn bar to rotate, coming into contact with said second surface of said web; and a shifting mechanism for horizontally moving said second roller.
 4. A noncontact web transporting apparatus according to claim 3, wherein the pair of said second rollers are disposed at symmetrical positions about said turn bar.
 5. A noncontact web transporting apparatus according to claim 4, wherein an interval of said second rollers is longer that an interval of said first rollers.
 6. A noncontact web transporting apparatus according to claim 5, wherein said jet openings formed in the jet surface of said turn bar are arranged in a zigzag state.
 7. A noncontact web transporting apparatus according to claim 6, wherein said jet surface has a U-shaped cross section in the transport direction of said web.
 8. A noncontact web transporting apparatus according to claim 7, wherein said turn bar is provided with a duct for supplying said gaseous matter to the inside thereof.
 9. A noncontact web transporting apparatus according to claim 7, wherein said gaseous matter is the air.
 10. A noncontact web transporting apparatus according to claim 9, wherein said web is a photosensitive printing plate. 